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TMRC

/tmerk'/ n. The Tech Model Railroad Club at MIT, one of
the wellsprings of hacker culture. The 1959 `Dictionary of
the TMRC Language' compiled by Peter Samson included several terms
which became basics of the hackish vocabulary (see esp. foo
and frob).
By 1962, TMRC's legendary layout was already a marvel of complexity
(and has grown in the thirty years since; all the features
described here are still present). The control system alone
featured about 1200 relays. There were scram switches located
at numerous places around the room that could be thwacked if
something undesirable was about to occur, such as a train going
full-bore at an obstruction. Another feature of the system was a
digital clock on the dispatch, board, which was itself something of
a wonder in those bygone days before cheap LEDS and seven-segment
displays (no model railroad can begin to approximate the scale
distances between towns and stations, so model railroad timetables
assume a fast clock so that it seems to take about the right amount
of time for a train to complete its journey). When someone hit a
scram switch the clock stopped and the display was replaced with the
word `FOO'; at TMRC the scram switches are therefore called `foo
switches'.
Steven Levy, in his book `Hackers' (see the Bibliography in
appendix C), gives a stimulating account of those early
years. TMRC's Power and Signals group included most of the early
PDP-1 hackers and the people who later bacame the core of the MIT
AI Lab staff. Thirty years later that connection is still very
much alive, and this lexicon accordingly includes a number of
entries from a recent revision of the TMRC Dictionary.